1. Field of the Invention
The present invention relates to a precast concrete panel (hereinafter referred to as a PC panel) for a composite floor, which panel is laid between beams, for example, and has its surface covered with post-placed concrete to form a floor slab. More particularly, the invention pertains to a PC panel for a composite floor which ensures transmission of in-plane shearing forces which develop between the panel and the post-placed concrete.
2. Description of the Prior Art
Heretofore there have been proposed a variety of PC panels for use in the construction of a floor slab of composite structure. For instance, in Japanese Utility Model Publication No. 52974/80 there is proposed a "composite floor panel" of a construction in which ribs are protrusively provided on the surface of a concrete panel and a shear connecter in the form of a protection is further provided on each rib. The ribs formed on the surface of the concrete panel extend in the transverse direction thereof and are spaced apart in its longitudinal direction, and the shearing connecters on the ribs are spaced apart in the transverse direction of the concrete panel.
In Japanese Patent Publication No. 6061/87 there is proposed a "floor panel constructing method" utilizing a PC panel of the type that has a plurality of concavities formed only in a peripheral portion of an upper part of the panel along beams, leaving the remaining central portion flat. The plurality of concavities are individually formed, that is, each is spaced apart from other concavities in the surface of the concrete panel, and are discontinuously arranged along the transverse and longitudinal directions of the panel. The area over which the concavities are arranged is limited to the peripheral portion of the upper part of the concrete panel along beams.
In Japanese Patent Publication No. 42766/87 there is proposed a "method of making a PC panel for a composite floor" for manufacturing a PC panel of the type wherein a number of concavities are discontinuously disposed on the surface of the panel. In this instance, all the concavities are formed in the concrete panel with the same depth and are isolated or spaced apart from each other.
The above-mentioned known PC panels are intended to solve different problems but what is important in common to them is whether or not they can surely transmit an in-plane shearing force which acts between the concrete panel and the post-placed concrete. From the viewpoint of shearing force transmission performance, the purpose of the first-mentioned PC panel is to ensure the transmission of the shearing force by forming protrusions or stepped portions such as ribs and projections on the surface of the concrete panel. As compared with the second- and third-mentioned PC panels, however, the PC panel of this type necessarily becomes heavier as it requires the formation of such protrusions while retaining the necessary mechanical strength (i.e. the thickness) of the concrete panel. Hence, the first-mentioned PC panel is considered to be more difficult to handle than the other known PC panels. It is considered preferable that the stepped portions to be formed on the concrete panel for transmitting the shearing force be provided in the form of concavities because they afford reduction of the weight of the concrete panel itself.
The second- and third-mentioned PC panels, both of which have concavities formed in the concrete panel for securing the transmission of the shearing force, are extremely similar to each other in the formation of the concavities and their arrangement except for the range over which the concavities are formed. Namely, each of these PC panels has a structure in which the concavities extend to a certain depth from the surface of the concrete panel and are discontinuously disposed in spaced apart relation to each other. In both of the above PC panels, the concavities are formed simply by boring the concrete surface to a fixed depth. The area over which the shearing force can be transmitted depends on the number of concavities formed or the size of each concavity. Meanwhile, a section loss of the concrete panel varies with the number of concavities formed. Thus, in order to ensure a sufficient surface area of the concrete panel with a small section loss, the number of concavities must be small. However, this results in an insufficient shearing force transmission performance. On the other hand, when the surface area of the concrete panel is reduced to increase the number of concavities, the shearing force can be transmitted sufficiently but the section loss becomes too large.